It's more than understandable that you crave for a Super Mario Bros. 3 desktop wallpaper. No, really. To grab the wallpapers posted above as well as a selection of some of the best retro-Mario desktops around simply follow these links: One, Two, Three, Four and Five.
Lovers of quality gaming and text adventures will absolutely love those (nine!) amazing Magnetic Scrolls wallpapers, that will let their desktops daily remind them of the brilliance of Wonderland, Corruption and Fish!
Posted a couple of years before the game's release, Ron Gilbert's Deathspank wallpapers are excellent, free and available in every resolution imaginable. Also, available in ascii and for EGA. Also, also, available for your iPhone.